Lithium ion cylindrical battery and electrochemical device

Abstract

The invention provides a cylindrical lithium ion battery and an electrochemical device, and relates to the technical field of lithium ion batteries. The cylindrical lithium ion battery comprises a shell and a battery roll core accommodated in the shell, the battery roll core is formed by winding a strip-shaped positive plate, a strip-shaped negative plate and a diaphragm between the strip-shaped positive plate and the strip-shaped negative plate, the strip-shaped positive plate comprises a covering positive active material layer area and a positive empty foil area, and the strip-shaped negative plate comprises a covering negative active material layer area and a negative empty foil area; the positive electrode empty foil area and the negative electrode empty foil area are perpendicular to the winding direction and are formed on the top end face or the bottom end face; the lithium ion cylindrical battery meets the following relational expressions in the charging and discharging processes: the discharging rate nC meets the condition that n is greater than or equal to 10; the discharge capacity satisfies Q2 / Q1 > = 60% and (Q2 / Q1) * n > = 6. Performance indexes are achieved in the charging and discharging process, so that the electrochemical device can still output considerable electric quantity and energy in a low-temperature environment.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium ion cylindrical battery and an electrochemical device. Background Art

[0002] In current battery applications, lithium-ion batteries are widely used. However, traditional lithium-ion batteries have many problems in low-temperature environments. Low temperatures significantly slow down the diffusion rate of lithium ions in positive and negative electrode materials, increase electrolyte viscosity, and reduce ion conductivity, which directly increases the internal resistance of the battery, and then the battery's charge and discharge capacity and output power are greatly reduced. Moreover, when charging at low temperatures, lithium precipitation is prone to occur, which not only accelerates the consumption of electrolyte and reduces the reversible capacity of the battery, but in severe cases, the growth of lithium dendrites may also pierce the battery diaphragm, causing an internal short circuit in the battery and causing serious safety accidents.

[0003] Therefore, developing a new type of low-temperature lithium-ion battery to meet the urgent demand for high-performance batteries in low-temperature environments such as outdoor equipment in cold regions and aerospace has become a key issue that needs to be urgently addressed in this field.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] A first object of the present invention is to provide a lithium-ion cylindrical battery having an extremely good discharge performance in a low temperature environment.

[0006] A second object of the present invention is to provide an electrochemical device comprising the lithium ion cylindrical battery.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] In a first aspect, the present invention provides a lithium-ion cylindrical battery, the lithium-ion cylindrical battery comprising a shell and a battery core contained in the shell; the battery core is wound by a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet and a separator therebetween, the strip-shaped positive electrode sheet comprises a positive electrode active material layer covering region and a positive electrode empty foil region, the strip-shaped negative electrode sheet comprises a negative electrode active material layer covering region and a negative electrode empty foil region, and the positive electrode empty foil region and the negative electrode empty foil region are both perpendicular to the winding direction and are formed on the top end face or the bottom end face;

[0009] And the lithium-ion cylindrical battery satisfies the following relationship during the charging and discharging process:

[0010] The discharge rate nC satisfies n≥10; the discharge capacity satisfies Q2 / Q1≥60%, and (Q2 / Q1)×n≥6;

[0011] Wherein, Q1 represents the discharge capacity of the lithium-ion cylindrical battery in the constant current discharge operation when the lithium-ion cylindrical battery with 100% SOC is placed at an ambient temperature of 25°C for more than 6 hours and then discharged at a discharge rate of 0.5C until the voltage of the lithium-ion cylindrical battery drops to 2.5V;

[0012] Wherein, Q2 represents the discharge capacity of the lithium-ion cylindrical battery in the constant current discharge operation when the lithium-ion cylindrical battery with 100% SOC is placed at an ambient temperature T for more than 6 hours, the lithium-ion cylindrical battery is discharged at a discharge rate nC at the ambient temperature T, and the discharge operation is continued until the voltage of the lithium-ion cylindrical battery drops to 1.5V and / or the temperature rises to 65°C; and the ambient temperature T satisfies -30°C≤T≤0°C.

[0013] Furthermore, (Q2 / Q1)×n≥10.

[0014] Furthermore, the lithium-ion cylindrical battery also includes an electrolyte contained in the shell.

[0015] Furthermore, the electrolyte includes lithium hexafluorophosphate, ethyl acetate and a solvent.

[0016] Furthermore, the electrolyte comprises, by mass percentage, 10-20% lithium hexafluorophosphate, 0.1-20% ethyl acetate, and the remainder being solvent.

[0017] Furthermore, the solvent is selected from any one of ethylene carbonate, ethyl methyl carbonate or diethyl carbonate or a combination of at least two thereof, preferably a combination of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.

[0018] Furthermore, the strip-shaped positive electrode sheet includes a positive electrode collector and a positive electrode active material coating located on at least one surface of the positive electrode collector, and the positive electrode collector includes a positive electrode active material coating area and a positive electrode active material uncoated area; the strip-shaped negative electrode sheet includes a negative electrode collector and a negative electrode active material coating located on at least one surface of the negative electrode collector, and the negative electrode collector includes a negative electrode active material coating area and a negative electrode active material uncoated area.

[0019] Furthermore, the uncoated area of ​​the positive active material occupies 1 to 12% of the surface area of ​​the positive current collector; and the uncoated area of ​​the negative active material occupies 1 to 10% of the surface area of ​​the negative current collector.

[0020] Furthermore, the positive electrode active material coating comprises a positive electrode active material, a binder and a conductive agent.

[0021] Furthermore, the positive electrode active material coating comprises, by mass percentage, 95-97% of positive electrode active material, 1.5-3% of binder and 1.5-3% of conductive agent.

[0022] Furthermore, the positive electrode active material is selected from a composite metal oxide of one or more of the group consisting of cobalt, manganese, aluminum and nickel and lithium, preferably lithium nickel cobalt manganese oxide.

[0023] Furthermore, in the positive electrode active material, the content of nickel atoms accounts for more than 75% of the total content of all transition metal atoms.

[0024] Furthermore, the chemical formula of the lithium nickel cobalt manganese oxide is Li a Ni x Co y Mn z O b ; Among them, 0.7≤x≤0.95, 0.01≤y≤0.1, 0.01≤z≤0.1, 1.8≤b≤2.2, 0.9≤a≤1.1.

[0025] Furthermore, the binder is selected from any one of polyvinylidene fluoride, polyethylene glycol, polymethyl methacrylate or polyvinyl acetate, or a combination of at least two thereof.

[0026] Furthermore, the conductive agent is selected from carbon nanotubes and / or acetylene black.

[0027] Furthermore, at least one edge of the positive electrode active material coating region has an inorganic ceramic coating region.

[0028] Furthermore, the inorganic ceramic coating includes inorganic material particles.

[0029] Furthermore, the inorganic material particles are selected from any one or a combination of at least two of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron oxide, boehmite, gypsum, talc or calcite.

[0030] Furthermore, the average particle size Dv50 of the inorganic material particles is between 0.6 and 5 μm.

[0031] Furthermore, along the width direction of the positive electrode sheet, the width of the inorganic ceramic coating accounts for 1-5% of the width of the entire positive electrode sheet.

[0032] Furthermore, the negative electrode active material coating comprises a negative electrode active material, a binder and a conductive agent.

[0033] Furthermore, the negative electrode active material coating comprises, by mass percentage, 92-96% of negative electrode active material, 1-4% of binder and 1-4% of conductive agent;

[0034] Furthermore, the negative electrode active material includes any one of artificial graphite, natural graphite, silicon-oxygen material or silicon-carbon material, or a combination of at least two thereof.

[0035] Furthermore, in the negative electrode active material, the mass of silicon element accounts for 1 to 20% of the total mass of the negative electrode active material.

[0036] Furthermore, the binder is selected from any one of polyacrylic acid, sodium carboxymethyl cellulose or styrene-butadiene rubber, or a combination of at least two thereof.

[0037] Furthermore, the conductive agent is selected from carbon nanotubes and / or acetylene black.

[0038] Furthermore, the battery roll core is a cylindrical battery roll core.

[0039] Wherein, the diameter of the cylindrical battery roll core is 10 to 50 mm, preferably 16 to 22 mm.

[0040] The height of the cylindrical battery core is 30 to 150 mm, preferably 64 to 130 mm.

[0041] Furthermore, the rated capacity of the lithium-ion cylindrical battery is 4000-6000 mAh.

[0042] Furthermore, the AC internal resistance of the lithium-ion cylindrical battery is less than 10 mΩ, and more preferably the AC internal resistance is ≤ 4 mΩ.

[0043] In a second aspect, the present invention provides an electrochemical device, wherein the electrochemical device comprises the lithium-ion cylindrical battery as described in the first aspect.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The unique structural design of the lithium-ion cylindrical battery of the present invention helps to optimize the electric field distribution and ion transmission path inside the battery, thereby improving the overall performance of the battery.

[0046] (2) The present invention matches the unique structure of the lithium-ion cylindrical battery with the electrolyte, so that it has excellent low-temperature discharge performance, that is, it can still output considerable power and energy in a low-temperature environment, greatly expanding its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 This is a schematic structural diagram of the lithium-ion cylindrical battery provided by the present invention.

[0049] Among them, 1 is the shell, 2 is the positive terminal, and 3 is the negative terminal.

[0050] Figure 2 A schematic structural diagram of a battery roll core accommodated in the housing provided by the present invention.

[0051] Among them, 4 is a battery roll core, 5 is a strip-shaped positive electrode sheet, 6 is a strip-shaped negative electrode sheet, and 7 is a separator.

[0052] Figure 3 This is a schematic structural diagram of the strip positive electrode sheet provided by the present invention.

[0053] Among them, 51 is the positive electrode active material coating area, 52 is the positive electrode active material uncoated area, and 53 is the inorganic ceramic coating area.

[0054] Figure 4 This is a schematic structural diagram of the strip-shaped negative electrode sheet provided by the present invention.

[0055] Among them, 61 is the positive electrode active material coating area, and 62 is the positive electrode active material uncoated area.

[0056] Figure 5 This is a schematic diagram of the structure of the strip positive electrode provided for Comparative Example 1.

[0057] Among them, 51 is the positive electrode active material coating area, 52 is the positive electrode active material uncoated area, and 54 is the positive electrode ear.

[0058] Figure 6 This is a schematic diagram of the structure of the strip-shaped negative electrode sheet provided for Comparative Example 1.

[0059] Among them, 61 is the negative electrode active material coating area, 62 is the negative electrode active material uncoated area, and 64 is the negative electrode ear. DETAILED DESCRIPTION

[0060] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] In a first aspect, the present invention provides a lithium-ion cylindrical battery, the lithium-ion cylindrical battery comprising a shell and a battery core contained in the shell; the battery core is wound by a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet and a separator therebetween, the strip-shaped positive electrode sheet comprises a positive electrode active material layer covering region and a positive electrode empty foil region, the strip-shaped negative electrode sheet comprises a negative electrode active material layer covering region and a negative electrode empty foil region, and the positive electrode empty foil region and the negative electrode empty foil region are both perpendicular to the winding direction and are formed on the top end face or the bottom end face;

[0062] And the lithium-ion cylindrical battery satisfies the following relationship during the charging and discharging process:

[0063] The discharge rate nC satisfies n≥10; the discharge capacity satisfies Q2 / Q1≥60%, and (Q2 / Q1)×n≥6;

[0064] Wherein, Q1 represents the discharge capacity of the lithium-ion cylindrical battery in the constant current discharge operation when the lithium-ion cylindrical battery with 100% SOC is placed at an ambient temperature of 25°C for more than 6 hours and then discharged at a discharge rate of 0.5C until the voltage of the lithium-ion cylindrical battery drops to 2.5V;

[0065] Wherein, Q2 represents the discharge capacity of the lithium-ion cylindrical battery in the constant current discharge operation when the lithium-ion cylindrical battery with 100% SOC is placed at an ambient temperature T for more than 6 hours, the lithium-ion cylindrical battery is discharged at a discharge rate nC at the ambient temperature T, and the discharge operation is continued until the voltage of the lithium-ion cylindrical battery drops to 1.5V and / or the temperature rises to 65°C; and the ambient temperature T satisfies -30°C≤T≤0°C.

[0066] It should be noted that the present invention provides a lithium ion cylindrical battery, such as Figure 1 As shown, the lithium-ion cylindrical battery includes a shell 1, a positive terminal 2 and a positive electrode column 3.

[0067] like Figure 2 As shown, the structure of the battery core contained in the shell provided by the present invention, the battery core 4 is wound by a strip-shaped positive electrode sheet 5, a strip-shaped negative electrode sheet 6 and a separator 7 therebetween.

[0068] like Figure 3As shown, the strip positive electrode sheet includes a positive electrode active material layer covering area and a positive electrode empty foil area. More specifically, the positive electrode active material layer covering area can refer to the positive electrode active material coated area 51, and the positive electrode empty foil area can refer to the positive electrode active material uncoated area 52.

[0069] like Figure 4 As shown, the strip-shaped negative electrode sheet includes a region covered with a negative electrode active material layer and a negative electrode empty foil region. More specifically, the region covered with a negative electrode active material layer may refer to a negative electrode active material coated region 61 , and the negative electrode empty foil region may refer to a negative electrode active material uncoated region 62 .

[0070] like Figure 2 and Figure 3 and Figure 4 As shown in the combination, the empty foil area of ​​the positive electrode sheet is perpendicular to the winding direction and can be formed on the top end face of the battery by flattening or cutting and stacking, while the empty foil area of ​​the negative electrode sheet is also perpendicular to the winding direction and can be formed on the bottom end face of the battery by flattening or cutting and stacking. The advantage of this structure over the traditional method of flattening or cutting and stacking is that the area of ​​the empty foil area can be significantly increased without the need for additional welding of the pole ear. And the unique structural design of the present invention helps to optimize the electric field distribution and ion transmission path inside the battery, and improve the overall performance of the battery.

[0071] As an optional implementation, the ambient temperature T satisfies -30°C≤T≤0°C, and the values ​​of the ambient temperature T include but are not limited to -30°C, -25°C, -20°C, -15°C, -10°C, -50°C, etc.

[0072] As an optional implementation, the discharge rate nC satisfies n≥10, and the discharge rate nC includes but is not limited to 10C, 10.5C, 11C, 11.5C, 12C, 12.5C, 13C, 13.5C, 14C, 14.5C, 15C, 16C, 17C, 18C, 19C, 20C, etc.

[0073] As an optional embodiment, the discharge capacity satisfies Q2 / Q1≥60%, and Q2 / Q1 values ​​include but are not limited to 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 101%, 102%, 103%, 104%, 105%, etc.

[0074] As an optional implementation, (Q2 / Q1)×n≥6, and the values ​​of (Q2 / Q1)×n include but are not limited to 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc.

[0075] It should be noted that the lithium-ion cylindrical battery satisfies the above relationship during the charging and discharging process. The realization of this performance index enables the electrochemical device to still output considerable power and energy in a low temperature environment, greatly expanding its application range.

[0076] As a preferred embodiment, (Q2 / Q1)×n≥10.

[0077] As an optional embodiment, the lithium-ion cylindrical battery further includes an electrolyte contained in the shell.

[0078] As an optional implementation, the electrolyte includes lithium hexafluorophosphate, ethyl acetate and a solvent.

[0079] As an optional implementation, the electrolyte includes, by mass percentage, 10-20% lithium hexafluorophosphate, 0.1-20% ethyl acetate, and the remainder being a solvent.

[0080] As an optional embodiment, based on the total mass of the electrolyte as 100%, the content of lithium hexafluorophosphate is 10-20%, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0081] As an optional embodiment, based on the total mass of the electrolyte as 100%, the content of ethyl acetate is 0.1-20%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0082] As a preferred embodiment, the electrolyte comprises, by mass percentage, 12-20% lithium hexafluorophosphate, 5-20% ethyl acetate, and the remainder is a solvent. The limited proportion of lithium hexafluorophosphate and the additive ethyl acetate can significantly improve the low-temperature charge and discharge performance of the lithium-ion cylindrical battery of the present application.

[0083] As an optional embodiment, the solvent is selected from any one of ethylene carbonate, ethyl methyl carbonate or diethyl carbonate, or a combination of at least two thereof.

[0084] As an optional embodiment, the solvent is a combination of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.

[0085] As an optional embodiment, the strip-shaped positive electrode sheet includes a positive electrode collector and a positive electrode active material coating located on at least one surface of the positive electrode collector, and the positive electrode collector includes a positive electrode active material coating area and a positive electrode active material uncoated area; the strip-shaped negative electrode sheet includes a negative electrode collector and a negative electrode active material coating located on at least one surface of the negative electrode collector, and the negative electrode collector includes a negative electrode active material coating area and a negative electrode active material uncoated area.

[0086] As an optional embodiment, the uncoated area of ​​the positive active material occupies 1 to 12% of the surface area of ​​the positive electrode collector, for example, it may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc.

[0087] As an optional embodiment, the uncoated area of ​​the negative active material occupies 1-10% of the surface area of ​​the negative current collector, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0088] As an optional implementation, the positive electrode active material coating layer includes a positive electrode active material, a binder and a conductive agent.

[0089] As an optional implementation, the positive electrode active material coating comprises, by mass percentage, 95-97% of positive electrode active material, 1.5-3% of binder and 1.5-3% of conductive agent.

[0090] Taking the total content of the positive electrode active material coating as 100%, the content of the positive electrode active material contained therein is 95-97%, for example, it can be 95%, 95.5%, 96%, 96.5%, 97%, etc.

[0091] Taking the total content of the positive electrode active material coating as 100%, the content of the binder is 1.5-3%, for example, 1.5%, 1.6%, 1.7%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, etc.

[0092] Taking the total content of the positive electrode active material coating as 100%, the content of the conductive agent is 1.5-3%, for example, 1.5%, 1.6%, 1.7%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, etc.

[0093] As an optional embodiment, the positive electrode active material is a composite metal oxide of one or more selected from the group consisting of cobalt, manganese, aluminum and nickel and lithium, preferably lithium nickel cobalt manganese oxide.

[0094] As an optional embodiment, in the positive electrode active material, the content of nickel atoms accounts for more than 75% of the total content of all transition metal atoms, for example, it can be 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, etc.

[0095] As a preferred embodiment, in the positive electrode active material, the content of nickel atoms accounts for more than 79% of the total content of all transition metal atoms.

[0096] As an optional embodiment, the chemical formula of the lithium nickel cobalt manganese oxide is Li a Ni x Co y Mn z O b ; Among them, 0.7≤x≤0.95, 0.01≤y≤0.1, 0.01≤z≤0.1, 1.8≤b≤2.2, 0.9≤a≤1.1.

[0097] As an optional embodiment, in the positive electrode active material coating, the binder is selected from any one of polyvinylidene fluoride, polyethylene glycol, polymethyl methacrylate or polyvinyl acetate, or a combination of at least two thereof.

[0098] As an optional embodiment, in the positive electrode active material coating, the conductive agent is selected from carbon nanotubes and / or acetylene black.

[0099] As an optional embodiment, at least one edge of the positive electrode active material coating region has an inorganic ceramic coating region.

[0100] As an optional embodiment, the inorganic ceramic coating includes inorganic material particles.

[0101] As an optional embodiment, the inorganic material particles are selected from any one or a combination of at least two of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron oxide, boehmite, gypsum, talc or calcite.

[0102] As an optional embodiment, the average particle size Dv50 of the inorganic material particles is between 0.6 and 5 μm, for example, it can be 0.6 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0103] As an optional embodiment, along the width direction of the positive electrode sheet, the width of the inorganic ceramic coating accounts for 1-5% of the width of the entire positive electrode sheet, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0104] As an optional implementation, the negative electrode active material coating layer includes a negative electrode active material, a binder and a conductive agent.

[0105] As an optional implementation, the negative electrode active material coating comprises, by mass percentage, 92-96% of negative electrode active material, 1-4% of binder and 1-4% of conductive agent.

[0106] As an optional embodiment, the negative electrode active material includes any one of artificial graphite, natural graphite, silicon-oxygen material or silicon-carbon material, or a combination of at least two thereof.

[0107] As an optional embodiment, in the negative electrode active material, the mass of silicon element accounts for 1 to 20% of the total mass of the negative electrode active material, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0108] As a preferred embodiment, in the negative electrode active material, the mass of silicon element accounts for 4 to 20% of the total mass of the negative electrode active material.

[0109] As an optional embodiment, the binder is selected from any one of polyacrylic acid, sodium carboxymethyl cellulose or styrene-butadiene rubber, or a combination of at least two thereof.

[0110] As an optional implementation, the conductive agent is selected from carbon nanotubes and / or acetylene black.

[0111] As an optional implementation, the battery roll core is a cylindrical battery roll core.

[0112] As an optional embodiment, the diameter of the cylindrical battery roll core is 10 to 50 mm, for example, it can be 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 21 mm, 24 mm, 26 mm, 28 mm, 30 mm, 32 mm, 33 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm, 50 mm, etc.

[0113] As a preferred embodiment, the diameter of the cylindrical battery roll core is 16 to 22 mm.

[0114] As an optional embodiment, the height of the cylindrical battery roll core is 30 to 150 mm, for example, it can be 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm, etc.

[0115] As a preferred embodiment, the height of the cylindrical battery core is 64 to 130 mm.

[0116] As an optional embodiment, the rated capacity of the lithium-ion cylindrical battery is 4000-6000mAh, for example, it can be 4000mAh, 4200mAh, 4400mAh, 4500mAh, 4600mAh, 4800mAh, 5000mAh, 5200mAh, 5400mAh, 5500mAh, 5600mAh, 5800mAh, 6000mAh, etc.

[0117] As an optional embodiment, the AC internal resistance of the lithium-ion cylindrical battery is less than 10mΩ, for example, it can be 9.9mΩ, 9.5mΩ, 9mΩ, 8.5mΩ, 8mΩ, 7.5mΩ, 7mΩ, 6.5mΩ, 6mΩ, 5.5mΩ, 5mΩ, 4.5mΩ, 4mΩ, 3.9mΩ, 3.8mΩ, 3.6mΩ, 3.5mΩ, 3.4mΩ, 3.2mΩ, 3.1mΩ, 3.0mΩ, 2.9mΩ, 2.8mΩ, 2.6mΩ, 2.5mΩ, etc.

[0118] As a preferred embodiment, the AC internal resistance of the lithium-ion cylindrical battery is ≤4mΩ, for example, it can be 3.9mΩ, 3.8mΩ, 3.6mΩ, 3.5mΩ, 3.4mΩ, 3.2mΩ, 3.1mΩ, 3.0mΩ, 2.9mΩ, 2.8mΩ, 2.6mΩ, 2.5mΩ, etc.

[0119] In a second aspect, the present invention provides an electrochemical device, wherein the electrochemical device comprises the lithium-ion cylindrical battery as described in the first aspect.

[0120] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0121] The discharge characteristic test method in the following embodiments is: the electrochemical device with 100% SOC is placed at an ambient temperature of 25°C for more than 6 hours, and then a discharge operation is performed at a discharge rate of 0.5C until the voltage of the electrochemical device drops to 2.5V, and the discharge capacity of the electrochemical device in the constant current discharge operation is Q1; the electrochemical device with 100% SOC is placed at an ambient temperature of T for more than 6 hours, and at the ambient temperature T, a discharge operation is performed on the electrochemical device at a discharge rate of nC, and the discharge operation is continued until the voltage of the electrochemical device drops to 1.5V or the device temperature rises to 65°C, and the discharge capacity of the electrochemical device in the constant current discharge operation is Q2.

[0122] Example 1

[0123] The present embodiment provides a lithium-ion cylindrical battery, which comprises a shell and a battery core contained in the shell; the battery core is formed by winding a strip-shaped positive electrode sheet and a strip-shaped negative electrode sheet stacked via a separator; wherein the strip-shaped positive electrode sheet has a positive electrode active material layer covering the positive electrode and an empty foil area, and the positive electrode empty foil area accounts for 7.8% of the surface area of ​​the positive electrode collector, and the strip-shaped negative electrode sheet also has a negative electrode active material layer covering the empty foil area, and the negative electrode empty foil area accounts for 6.6% of the surface area of ​​the negative electrode collector; wherein the empty foil area of ​​the positive electrode sheet is perpendicular to the winding direction and is formed by flattening to form the top end face of the battery, and the empty foil area of ​​the negative electrode sheet is perpendicular to the winding direction and is formed by flattening to form the bottom end face of the battery.

[0124] The lithium ion cylindrical battery is prepared by the following steps:

[0125] (1) Positive electrode

[0126] The composition of the positive electrode plate: the positive electrode plate includes a positive electrode current collector aluminum foil and a positive electrode coating coated on both sides of the aluminum foil; wherein, calculated by mass percentage, the positive electrode coating includes 95.5% LiNi 0.83 Co 0.07 Mn 0.06 Al 0.04 O2, 0.5% carbon nanotube conductive agent, 2.5% Super-P (conductive carbon black) conductive agent and 1.5% polyvinylidene fluoride PVDF binder;

[0127] Preparation steps of the positive electrode sheet: add the raw materials in the above-mentioned positive electrode coating into N-methylpyrrolidone and stir to form a positive electrode slurry with a solid content of 60wt%, and then apply the positive electrode slurry on the positive electrode collector aluminum foil, and ensure that the uncoated area occupies 7.8% of the surface area of ​​the positive electrode collector to form a positive electrode sheet.

[0128] (2) Negative electrode

[0129] The composition of the negative electrode plate: the negative electrode plate comprises a negative electrode current collector copper foil and a negative electrode coating coated on both sides of the copper foil; wherein, calculated by mass percentage, the negative electrode coating comprises 91% artificial graphite, 5% silicon, 1.2% conductive agent acetylene black, and 2.8% negative electrode binder polyacrylic acid;

[0130] The preparation steps of the negative electrode plate are as follows: the raw materials in the above-mentioned negative electrode coating are added into deionized water and stirred to form a negative electrode slurry with a solid content of 40wt%, which is coated on the negative electrode collector copper foil and ensures that the uncoated area accounts for 6.6% of the surface area of ​​the negative electrode collector; and a negative electrode plate is formed.

[0131] (3) Preparation of electrolyte

[0132] The composition of the electrolyte: calculated by mass percentage, the electrolyte includes 18.1% lithium hexafluorophosphate, 18% ethyl acetate, and the remainder is a solvent; the solvent is a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 1:1:1;

[0133] The preparation steps of the electrolyte are as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried lithium hexafluorophosphate is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 18.1wt%, and ethyl acetate as an additive is added to account for 18wt% of the total mass of the electrolyte.

[0134] (4) The diaphragm

[0135] The composition of the diaphragm includes a high-porous dynamic diaphragm, a base film PE with a thickness of 10 μm, a ceramic coating with a thickness of 1 μm on both sides, and a PVDF coating with a thickness of 1 μm. The air permeability of the diaphragm is 100s / 100mL.

[0136] (5) Assembly of lithium-ion cylindrical batteries:

[0137] The positive electrode sheet and the negative electrode sheet are rolled, slit and die-cut respectively, and then wound together with the separator. The positive electrode sheet, the negative electrode sheet and the separator are wound by a winding machine to form a roll core, and the positive electrode tabs and the negative electrode tabs are cut and stacked on the roll core. Then, the positive bus bar and the negative bus bar are welded to the roll core respectively, and then the negative bus bar is welded to the steel shell. An insulating sheet is placed on the top of the positive bus bar, and the positive bus bar is welded to the cap to obtain a lithium-ion battery roll core body, which is loaded into a cylindrical battery shell. After completing the injection, sealing and formation processes, the 21700 cylindrical lithium-ion battery is obtained. The battery has a diameter of 21 mm, a height of 70 mm, and a battery capacity of 4.0 Ah.

[0138] The test data of the lithium-ion cylindrical battery provided in this embodiment during the charge and discharge process are shown in Table 1 below:

[0139] Table 1

[0140]

[0141] Example 2

[0142] This embodiment provides a lithium ion cylindrical battery, which is different from the embodiment 1 only in that the content of ethyl acetate is reduced to 6 wt %.

[0143] The test data of the lithium-ion cylindrical battery provided in this embodiment during the charge and discharge process are shown in Table 2 below:

[0144] Table 2

[0145]

[0146]

[0147] Example 3

[0148] This embodiment provides a lithium ion cylindrical battery, which is different from the embodiment 1 only in that the content of lithium hexafluorophosphate is reduced to 12.5%, and the content of ethyl acetate is reduced to 15 wt %.

[0149] The test data of the lithium-ion cylindrical battery provided in this embodiment during the charge and discharge process are shown in Table 3 below:

[0150] Table 3

[0151]

[0152] Example 4

[0153] This embodiment provides a lithium-ion cylindrical battery, which is different from Embodiment 1 only in that an inorganic ceramic coating area is provided at one edge of the positive electrode sheet; the inorganic ceramic coating includes inorganic material particles, which, calculated by mass percentage, include: 10% aluminum oxide and 90% boehmite; and the average particle size Dv50 of the inorganic material particles is 1.2 μm; and along the width direction of the positive electrode sheet, the width of the inorganic ceramic coating accounts for 4.5% of the width of the entire positive electrode sheet.

[0154] The test data of the lithium-ion cylindrical battery provided in this embodiment during the charge and discharge process are shown in Table 4 below:

[0155] Table 4

[0156]

[0157] Example 5

[0158] This embodiment provides a lithium-ion cylindrical battery, which is different from Embodiment 1 only in that the strip-shaped positive electrode sheet has a covering positive electrode active material layer and an empty foil area, and the positive electrode empty foil area accounts for 6.8% of the surface area of ​​the positive electrode collector, and the strip-shaped negative electrode sheet also has a covering negative electrode active material layer and an empty foil area, and the negative electrode empty foil area accounts for 5.6% of the surface area of ​​the negative electrode collector.

[0159] The test data of the lithium-ion cylindrical battery provided in this embodiment during the charge and discharge process are shown in Table 5 below:

[0160] Table 5

[0161]

[0162] Example 6

[0163] This embodiment provides a lithium-ion cylindrical battery, which is different from Embodiment 1 only in that the strip-shaped positive electrode sheet has a covering positive electrode active material layer and an empty foil area, and the positive electrode empty foil area accounts for 8.8% of the surface area of ​​the positive electrode collector, and the strip-shaped negative electrode sheet also has a covering negative electrode active material layer and an empty foil area, and the negative electrode empty foil area accounts for 7.6% of the surface area of ​​the negative electrode collector.

[0164] The test data of the lithium-ion cylindrical battery provided in this embodiment during the charge and discharge process are shown in Table 6 below:

[0165] Table 6

[0166]

[0167] As shown in the above embodiments, the empty foil area of ​​the positive electrode sheet is perpendicular to the winding direction and can be formed on the top end face of the battery by flattening or cutting and stacking, while the empty foil area of ​​the negative electrode sheet is also perpendicular to the winding direction and can be formed on the bottom end face of the battery by flattening or cutting and stacking. The advantage of this structure over the traditional method of flattening or cutting and stacking is that the area of ​​the empty foil area can be significantly increased without the need for additional welding of the pole ear. And the unique structural design of the present invention helps to optimize the electric field distribution and ion transmission path inside the battery, and improve the overall performance of the battery.

[0168] The lithium-ion cylindrical batteries provided in the above embodiments satisfy the following relationship during the charge and discharge process: the discharge rate nC satisfies n≥10; the discharge capacity satisfies Q2 / Q1≥60%, and (Q2 / Q1)×n≥6; the realization of this performance indicator enables the electrochemical device to still output considerable power and energy in a low temperature environment, greatly expanding its application range.

[0169] Comparative Example 1

[0170] This comparative example provides a lithium-ion cylindrical battery, which is different from Example 1 only in that the battery core is arranged differently, and the battery core adopts a traditional double-pole ear method.

[0171] like Figure 5 As shown, the positive electrode sheet has a positive electrode active material coating area and a positive electrode active material uncoated area, as well as a positive electrode ear welded to the positive electrode active material uncoated area, and the positive electrode active material uncoated area is arranged between the two parts of the positive electrode active material coating area and arranged parallel to the winding direction.

[0172] like Figure 6 As shown, the negative electrode sheet has a negative electrode active material coating area and a negative electrode active material uncoated area, and a positive electrode ear welded to the negative electrode active material uncoated area, and the negative electrode active material uncoated area is respectively arranged on both sides of the edge of the negative electrode active material coating area and is arranged parallel to the winding direction.

[0173] The test data of the lithium-ion cylindrical battery provided in this comparative example during the charge and discharge process are shown in Table 7 below:

[0174] Table 7

[0175]

[0176] The lithium-ion cylindrical battery provided in the above-mentioned comparative example 1 adopts the traditional bipolar ear method, and the area of ​​the empty foil area of ​​the positive and negative electrode sheets is obviously much smaller than the battery cell formed by the full-electrode ear method provided in Example 1, and its discharge capacity during charging and discharging cannot meet the requirements of Q2 / Q1≥60%, and (Q2 / Q1)×n≥10, so that the power and energy of the lithium-ion cylindrical battery are reduced in a low temperature environment.

[0177] Comparative Example 2

[0178] This comparative example provides a lithium ion cylindrical battery, which is different from Example 1 only in that ethyl acetate is not added to the electrolyte.

[0179] The test data of the lithium-ion cylindrical battery provided in this comparative example during the charge and discharge process are shown in Table 8 below:

[0180] Table 8

[0181]

[0182] The electrolyte in the lithium-ion cylindrical battery provided in the above comparative example 2 does not contain additives, so its discharge capacity during charging and discharging cannot meet the requirements of Q2 / Q1≥60% and (Q2 / Q1)×n≥10, resulting in reduced power and energy of the lithium-ion cylindrical battery in a low temperature environment.

[0183] Comparative Example 3

[0184] This comparative example provides a lithium ion cylindrical battery, which is different from Example 1 only in that the content of lithium hexafluorophosphate is reduced to 10% and the content of ethyl acetate is reduced to 15wt%.

[0185] The test data of the lithium-ion cylindrical battery provided in this comparative example during the charge and discharge process are shown in Table 9 below:

[0186] Table 9

[0187]

[0188] The contents of lithium hexafluorophosphate and ethyl acetate in the lithium-ion cylindrical battery provided in the above comparative example 3 are not within the preferred range of the present application. Therefore, the discharge capacity during the charge and discharge process cannot meet the requirements of Q2 / Q1≥60% and (Q2 / Q1)×n≥10, resulting in reduced power and energy of the lithium-ion cylindrical battery in a low temperature environment.

[0189] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium-ion cylindrical battery, characterized in that: The lithium-ion cylindrical battery comprises a shell and a battery core contained in the shell; the battery core is wound by a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet and a separator therebetween, the strip-shaped positive electrode sheet comprises a positive electrode active material layer covering region and a positive electrode empty foil region, the strip-shaped negative electrode sheet comprises a negative electrode active material layer covering region and a negative electrode empty foil region, and the positive electrode empty foil region and the negative electrode empty foil region are both perpendicular to the winding direction and formed on the top end face or the bottom end face; And the lithium-ion cylindrical battery satisfies the following relationship during the charging and discharging process: The discharge rate nC satisfies n≥10; the discharge capacity satisfies Q2 / Q1≥60%, and (Q2 / Q1)×n≥6; Wherein, Q1 represents the discharge capacity of the lithium-ion cylindrical battery in the constant current discharge operation when the lithium-ion cylindrical battery with 100% SOC is placed at an ambient temperature of 25°C for more than 6 hours and then discharged at a discharge rate of 0.5C until the voltage of the lithium-ion cylindrical battery drops to 2.5V; Wherein, Q2 represents the discharge capacity of the lithium-ion cylindrical battery in the constant current discharge operation when the lithium-ion cylindrical battery with 100% SOC is placed at an ambient temperature T for more than 6 hours, and the lithium-ion cylindrical battery is discharged at a discharge rate nC at the ambient temperature T, and the discharge operation is continued until the voltage of the lithium-ion cylindrical battery drops to 1.5V or the temperature rises to 65°C; and the ambient temperature T satisfies -30°C≤T≤0°C.

2. The lithium-ion cylindrical battery according to claim 1, characterized in that: The (Q2 / Q1)×n≥10.

3. The lithium-ion cylindrical battery according to claim 1, characterized in that: The lithium-ion cylindrical battery also includes an electrolyte contained in the housing; Preferably, the electrolyte comprises lithium hexafluorophosphate, ethyl acetate and a solvent; Preferably, the electrolyte comprises, by mass percentage: 10-20% lithium hexafluorophosphate, 0.1-20% ethyl acetate, and the remainder being solvent; Preferably, the solvent is selected from any one of ethylene carbonate, ethyl methyl carbonate or diethyl carbonate or a combination of at least two thereof, preferably a combination of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.

4. The lithium-ion cylindrical battery according to claim 1, characterized in that: The strip-shaped positive electrode sheet comprises a positive electrode current collector and a positive electrode active material coating located on at least one surface of the positive electrode current collector, and the positive electrode current collector comprises a positive electrode active material coating area and a positive electrode active material uncoated area; the strip-shaped negative electrode sheet comprises a negative electrode current collector and a negative electrode active material coating located on at least one surface of the negative electrode current collector, and the negative electrode current collector comprises a negative electrode active material coating area and a negative electrode active material uncoated area; Preferably, the uncoated area of ​​the positive active material occupies 1 to 12% of the surface area of ​​the positive current collector; and the uncoated area of ​​the negative active material occupies 1 to 10% of the surface area of ​​the negative current collector.

5. The lithium-ion cylindrical battery according to claim 4, characterized in that: The positive electrode active material coating comprises a positive electrode active material, a binder and a conductive agent; Preferably, the positive electrode active material coating comprises, by mass percentage, 95-97% of positive electrode active material, 1.5-3% of binder and 1.5-3% of conductive agent; Preferably, the positive electrode active material is selected from a composite metal oxide of one or more of the group consisting of cobalt, manganese, aluminum and nickel and lithium, preferably lithium nickel cobalt manganese oxide; Preferably, in the positive electrode active material, the content of nickel atoms accounts for more than 75% of the total content of all transition metal atoms; Preferably, the chemical formula of the lithium nickel cobalt manganese oxide is Li a Ni x Co y Mn z O b ; Among them, 0.7≤x≤0.95, 0.01≤y≤0.1, 0.01≤z≤0.1, 1.8≤b≤2.2, 0.9≤a≤1.1; Preferably, the binder is selected from any one of polyvinylidene fluoride, polyethylene glycol, polymethyl methacrylate or polyvinyl acetate, or a combination of at least two thereof; Preferably, the conductive agent is selected from carbon nanotubes and / or acetylene black.

6. The lithium-ion cylindrical battery according to claim 4, characterized in that: At least one edge of the positive electrode active material coating area has an inorganic ceramic coating area; Preferably, the inorganic ceramic coating comprises inorganic material particles; Preferably, the inorganic material particles are selected from any one or a combination of at least two of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron oxide, boehmite, gypsum, talc or calcite; Preferably, the average particle size Dv50 of the inorganic material particles is between 0.6 and 5 μm; Preferably, along the width direction of the positive electrode sheet, the width of the inorganic ceramic coating accounts for 1-5% of the width of the entire positive electrode sheet.

7. The lithium-ion cylindrical battery according to claim 4, characterized in that: The negative electrode active material coating comprises a negative electrode active material, a binder and a conductive agent; Preferably, the negative electrode active material coating comprises, by mass percentage, 92-96% of negative electrode active material, 1-4% of binder and 1-4% of conductive agent; Preferably, the negative electrode active material includes any one of artificial graphite, natural graphite, silicon-oxygen material or silicon-carbon material, or a combination of at least two thereof; Preferably, in the negative electrode active material, the mass of silicon element accounts for 1 to 20% of the total mass of the negative electrode active material; Preferably, the binder is selected from any one or a combination of at least two of polyacrylic acid, sodium carboxymethyl cellulose or styrene-butadiene rubber; Preferably, the conductive agent is selected from carbon nanotubes and / or acetylene black.

8. The lithium-ion cylindrical battery according to claim 1, characterized in that: The battery roll core is a cylindrical battery roll core; Wherein, the diameter of the cylindrical battery core is 10 to 50 mm, preferably 16 to 22 mm; The height of the cylindrical battery core is 30 to 150 mm, preferably 64 to 130 mm.

9. The lithium-ion cylindrical battery according to claim 1, characterized in that: The rated capacity of the lithium-ion cylindrical battery is 4000-6000 mAh; The AC internal resistance of the lithium-ion cylindrical battery is less than 10 mΩ, and more preferably the AC internal resistance is ≤ 4 mΩ.

10. An electrochemical device, characterized in that: The electrochemical device comprises the lithium ion cylindrical battery according to any one of claims 1 to 9.

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